Aircraft construction



June 3, 1941. l. H. D'RIGGS 2,244,357

' AIRCRAFT CONSTRUCTION Filed Nov. 4, 1959' .smr/o vs (12 .6) 15 I I l 1I Z24234567891MHQ Juan 1 33 Q arrow;

' not be avoided because of serving the trim.

' in large boats or effective leverage, the water on a comparativelysmall areajat the Patented .....3.1941- T 7 OFFICE,

Amour-"r consrauc'non Ivan ll. Briggs,

Ferguson, Ma, asdgnor Glenn L. Martin Company, Baltimore,

to The Md.

Application November 4, 1939, Serial No. 802,794 Claims. (Chill-86.5)

The present invention relates to flying boats and particularly to theconstruction of hull bottoms for such boats.

It is usual-in a flying the hull around the mid point thereof. Inoperating such a boat, during the take-oil, the control of the trimmingangle is quite difficult. At the low speeds at whichthe ing thetake-off, the elevators do not have their normal eifectiveness. For thatreason the boat ordinarily rides at a trimming angle considerablygreater than the angle of least resistance. Of course this high angle oftrim causes a considerable increase in resistance, but this increasecanboat to provide a step in the necessity for prefreely, so as to avoidany drag on the hull bottom itself when the boat is running on the firststep.

boat is moving dur- The primary object of the present invention is toconstruct'the hull in such a manner that by its movement through thewater a substantial force is exerted thereon which acts to aid,inkeeping the boat trimmed at a lesser angle, nearer to or equal to theangle of'least resistance. This of course reduces the trimming angle,and the resistance of the whole craft is reduced. Thus it is possible toaccelerate the boat more quickly and to achieve a shorter take-oil.

there is a tendency particularly to tip the boat backward, because ofthe large forces exerted on the front end thereof. Another object ofthis invention is to provide means at the rear of the hull which cause acounter moment so as to balance'at least in part this tendency. It is afurther object to provide means which have a long moment arm so that theforce exerted by ermore,

rear can balance the force exerted on .a larger area at the front.

ermore, when a flying boat is moving through the water, the water whichis thrown up over the after body creates a drag on the outer surface ofthe hull. Furthermore, this water is likely to get in the wake of thepropeller and to be thrown back on the tail, thus dirtying the. tail andpossibly obscuring the vision of observers situated therein. Anotherobject of the inven tion is to provide a hull of such construction thatthis spraying of the water'over the after is avoided, by laying down thespray and preventing it from rising up into the wake of the propellers.

Still another object of the invention is to provide a construction foraccomplishing this last result, in which the lateral spray from the mainstep in the hull bottom is permitted to escape These results areaccomplished by providing at the. rear of the main step a hull portionthe rear end of which is provided at its outer edges with a turned overportion suilicient to lay down the spray and prevent it from rising upinto contact with the after body and tail portion of the boat.

Further objects and-advantages of the invention will appear more fullyfrom the following descrpition, particularly when taken in conjunctio'nwith the drawing which forms a part there- 0 In the drawing:

Fig. 1 shows in side elevation the body of a flying boat embodying myinvention;

Fig. 2 is an enlarged view of the lower righthand portion of theaircraft shown in Fig. i;

Fig. 3 is a contour diagram of the bottom pors I tion of the hulllooking from the rear, showing the outline thereof in the differentstations i to l2 indicated on Fig. 1. g c

The aircraft includes a fuselage it supported by wings I8, and a hullII. A rearwardly extending portion 20 of the. fuselage is adapted tosupport the usual tail.

end of the hull of such an aircraft.

' According to the invention, the hull is provided intermediate itslength with a usual step 22. Behind this step, the hull bottom has thecontours shown in. lines I to ill of Fig. 3. At'the' contour it there isa secondsmall step 24, and

behind that is a small hull portion 28 which terminates in a point as at2., the shape of the intermediate part of portion 26 being a simple V asindicated by line Ii in Fig. 3.

The section 23 between the steps 22 and It is for the most part-of theordinary V shape, and

provided with a keel line II. At stations I to I, e

or throughoutfls'ubstantially half its length. the hullportion 23 ispreferably of substantially V shape, or, in other words, in any crosssection its outline isrepresented by two straight lines intersecting atthe keel line it. From station I to station II, on the other hand, whilethe central portion of the hull is of V shape, the outer edges thereofgradually 2 are turned down more and more, reaching the greatest degree,of inclination away from the principal planes of the hull bottom at thestep 24, or at station 10, thus forming a downwardly turned. edgeportion 34. At this point, as indicated-by, the line of dashes" markedT.T in Fig. 3, the tangent to thehull.

The present invention in- ,volves changes in the construction of the resbottom at the outer edge thereof is directed upwardly and inwardly, or,in other words, the hull bottom at this point is turned slightly overbeyond the horizontal. The important require ment of the invention isthat the portion of the hull at this point be turned downwardly from thenormal line of the V bottom, or, in other words, that the tangent to thehull at the edge thereof in any transverse plane should intersect thelongitudinal vertical plane of the boat at a point above the point ofintersection of the keel line with the same transverse plane.

The portion 26 behind the rear step 24 is preferably of normal V 'shape,as stated. above. From the point 28, the rear line of the body extendssubstantially directly upwardly as at 32.

The above construction accomplishes the results set forth in theintroduction. The spray which is normally sent. up at the rear of thehull bottom is by the downwardly curved edge portion 34 turned andflattened down onto the surface of the water, and is thus prevented fromspraying upwardly over the rear of the boat. On the other hand, when theboat is riding on the step. spray escaping from the bottom of theforward step 22 is able to escape outwardly and at an angle through thespace between stations I and 6, without being turned down and withoutcontacting with the rear hull portion, so that a drag on the boat duringthis stage of its movement is prevented.

At the same time, the turned over portion at the rear of the boatservesto make the force exerted by the water more effective at low speeds, soas to help to regulate the trimming angle and keep it as low aspossible, thereby lowering the resistance of the boat. This ef-. feet isaccomplished because the turned over portion retards the outward flow ofthe water, and causes the water as it flows outwardly to exert asubstantially greater lifting action on the rear end of the boat. Asthis point is located at a considerable distance behind the center ofgravity, the effective force exerted by the water is increased and thustends to balance the larger force exerted in the front of the boat on ashorter leverage arm about the center of gravity.

While I have described herein one embodiment of my invention I wish itto be understood that I do not intend to limit myself thereby exceptwithin the scope of the appended claims.

I claim:

1. In a flying boat, a downwardly convex hull having a step in anintermediate portion thereof and means on the rear part of the portionof the hull behind said step to deflect the spray, the front end of saidmeans being spaced rearwardly from the step by at least about half thelength of said portion so as to permit the escape of spray produced bythe step.

2. A flying boat comprising a body and a hull bottom, a step in anintermediate portion of the hull bottom, the forward part of the portionof hull bottom behind said step being of substantially V shape, and therear part thereof being of substantially V shape and having its edgesturned downwardly, so that tangents to the edges of such rear partintersect the vertical longitudinal plane of the hull bottom at pointsabove the keel line in the same transverse plane.

3. A flying boat comprising a body and a hull bottom, a step in anintermediate portion of the hull bottom, the forward part of the portionof hull bottom behind said step being of substantially V shape, and therear part thereof being of substantially V shape and having its edgesturned downwardly, so that tangents to the edges of such rear partintersect the vertical longitudinal plane of the hull bottom at pointsabove the keel line in the same transverse plane, a second step at therear of said portion behind the first step, and a small hull portion ofV shape behind said second step.

4. A flying boat comprising a body and a hull bottom, a step in anintermediate portion of the hull bottom, the forward part of the portionof hull bottom behind said step being of substantially V shape, and therear part thereof being of substantially V shape and having its edgesturned downwardly, so that tangents to the edges of such rear partintersect the vertical longitudinal plane of the hull bottom at pointsabove the keel line in the same transverse ,plane, a second step at therear of said portion behind the first step, and a small hull portion ofV shape behind said second step, said second step being of less verticaldimension than said first step.

5. A flying boat comprising a body and a hull bottom, a step in anintermediate portion of the hull bottom, the forward part of the portionof the hull bottom behind said step being convex, and the rear partthereof being convex and having its edges turned downwardly so thattangents to the edges of such rear partintersect the verticallongitudinal plane of the hull bottom at points above the keel line inthe same transverse plane.

' IVAN H, DRIGGS.

